The present invention relates to a method of forming silica-containing ceramic coatings on substrates such as electronic devices. These coatings can be used as hermetic and/or dielectric layers.
The use of hydrogen silsesquioxane derived ceramic coatings on substrates such as electronic devices is known in the art. For instance, Haluska et al. in U.S. Pat. No. 4,756,977 disclose a process for forming silica-containing coatings on substrates such as electronic devices. The process described therein involves applying a solution of hydrogen silsesquioxane resin on a substrate followed by heating the coated substrate in air at a temperature in the range of 200.degree.-1000.degree. C. Such processes, however, can damage heat sensitive substrates by the temperature and time necessary for ceramification.
Other methods for converting hydrogen silsesquioxane resin to silica-containing materials at lower temperatures are also known in the art. For instance, U.S. Pat. No. 4,847,162 describes the conversion of hydrogen silsesquioxane resin to nitrified silica by heating in ammonia. Similarly, U.S. Pat. No. 5,059,448 describes the use of rapid thermal processing to convert hydrogen silsesquioxane resin to a silica containing ceramic. Finally, U.S. Pat. Nos. 5,116,637, 5,336,532, 5,262,201 and 5,436,029 describe the use of amines, ozone, wet ammonia, and nitrous oxide, respectively, to assist in the conversion of hydrogen silsesquioxane resin to silica-containing materials. Despite the lower thermal exposure of these processes, temperature sensitive substrates can still be damaged. Moreover, these processes are complicated by the additional equipment and materials which are required.
The present inventors have now discovered that hydrogen silsesquioxane resin can be converted to silica-containing coatings without significantly heating the underlying substrate by using an electron beam.